The initial classification of adrenergic receptors into α- and β-families was first described by Ahlquist in 1948 (Ahlquist R P, “A Study of the Adrenergic Receptors,” Am. J. Physiol. 153:586-600 (1948)). Functionally, the α-adrenergic receptors were shown to be associated with most of the excitatory functions (vasoconstriction, stimulation of the uterus and pupil dilation). β-adrenergic receptors were implicated in vasodilation, bronchodilation and myocardial stimulation (Lands et al., “Differentiation of Receptor Systems Activated by Sympathomimetic amines,” Nature 214:597-598 (1967)). Since this early work, α-adrenergic receptors have been subdivided into α1- and α2-adrenergic receptors. Cloning and expression of α-adrenergic receptors have confirmed the presence of multiple subtypes of both α1-(α1A, α1B, α1D) and α2-(α2A, α2B, α2C) adrenergic receptors (Michel et al., “Classification of α1-Adrenoceptor Subtypes,” Naunyn-Schmiedeberg's Arch. Pharmacol, 352:1-10 (1995); Macdonald et al., “Gene Targeting—Homing in on α2-Adrenoceptor-Subtype Function,” TIPS, 18:211-219 (1997)).
Current therapeutic uses of α-2 adrenergic receptor drugs involve the ability of those drugs to mediate many of the physiological actions of the endogenous catecholamines. There are many drugs that act on these receptors to control hypertension, intraocular pressure, eye reddening and nasal congestion and induce analgesia and anesthesia.
α2 adrenergic receptors can be found in the rostral ventrolateral medulla, and are known to respond to the neurotransmitter norepinephrine and the antihypertensive drug clonidine to decrease sympathetic outflow and reduce arterial blood pressure (Bousquet et al., “Role of the Ventral Surface of the Brain Stem in the Hypothesive Action of Clonidine,” Eur. J. Pharmacol., 34:151-156 (1975); Bousquet et al., “Imidazoline Receptors: From Basic Concepts to Recent Developments,” 26:S1-S6 (1995)). Clonidine and other imidazolines also bind to imidazoline receptors (formerly called imidazoline-guanidinium receptive sites or IGRS) (Bousquet et al., “Imidazoline Receptors: From Basic Concepts to Recent Developments,” 26:S1-S6 (1995)). Some researchers have speculated that the central and peripheral effects of imidazolines as hypotensive agents may be related to imidazoline receptors (Bousquet et al., “Imidazoline Receptors: From Basic Concepts to Recent Developments,” 26:S1-S6 (1995); Reis et al., “The Imidazoline Receptor: Pharmacology, Functions, Ligands, and Relevance to Biology and Medicine,” Ann. N.Y. Acad. Sci., 763:1-703 (1995).
Compounds having adrenergic activity are well-known in the art and are described in numerous patents and scientific publications. It is generally known that adrenergic activity is useful for treating animals of the mammalian species, including humans, for curing or alleviating the symptoms and conditions of numerous diseases and conditions. In other words, it is generally accepted in the art that pharmaceutical compositions having an adrenergic compound or compounds as the active ingredient are useful for treating, among other things, glaucoma, chronic pain, migraines, heart failure, and psychotic disorders (e.g., schizophrenia).
For example, published PCT application WO 02/076950 discloses compounds having α2 agonist activity of the following general formula:
Other publications disclosing similar compounds includes WO 01/00586, WO 99/28300, U.S. Pat. No. 6,841,684 B2 and US 2003/0023098 A1.
Another class of compounds having α2-agonist properties is disclosed in U.S. Pat. No. 5,658,938, and has the following general formula:
wherein n=1-2, R1-R3 represent hydrogen, halogen hydroxy, alkyl or alkoxy, and R5 is hydrogen or alkyl.
Another class of compounds reported to have affinity for α2 receptors includes the following two compounds (Bagley et. al., Med. Chem. Res. 1994, 4:346-364):

It is also known that compounds having adrenergic activity, such as α2A agonists, may be associated with undesirable side effects. Examples of such side effects include hyper- and hypotension, sedation, locomotor activity, psychotic disorders (e.g., schizophrenia).
Another class of compounds reported to have affinity for α2 receptors includes the following two compounds (Miller et. al., J. Med. Chem. 1994, 37:2328-2333; J. Med. Chem. 1996, 39:3001-3013; J. Med. Chem. 1997, 37:3014-3024):

Another class of indane and tetrahyrdonaphthalene type compounds having α2-agonist properties is disclosed in PCT application WO 97/12874 and WO20040506356. This class has the following general formula:
wherein n=0-1, X is 1 or 2 carbon units, R4 is H, OH, alkyl, or alkoxy, R5 may be taken together with R4 to form a carbonyl, and R6-R8═H, OH, SH, alkyl, alkenyl, cycloalkyl, alkoxy, hydroxyalkyl, alkylthio, alkylthiol, halo, CF3, NO2, or alkylamino. This class specifically includes MPV-2426 (fadolmidine) and its prodrug esters:
wherein R is optionally substituted lower alkyl, aryl, cycloalkyl, heteroaryl, lower alkylamino, and saturated 5- or 6-membered heterocyclic groups containing 1 or 2 N atoms.
Further, other classes of compounds that exhibit functional selectivity for the alpha 2C receptor have been discovered. Application U.S. Ser. No. 11/508,458, filed Aug. 23, 2006, discloses indoline compounds that possess this activity and application U.S. Ser. No. 11/508,467, filed on the same date, describes morpholine compounds that are functionally selective of the alpha 2C receptor. CIP applications of these applications have been filed; the Ser. Nos. 11/705,673 and 11/705,683, both filed on Feb. 13, 2009.
Additional applications that have been filed by Schering-Plough and disclose alpha2C receptor agonists include applications WO 2008/100480 (PCT/US2008/001808); WO 2008/100459 (PCT/US2008/001770) and WO 2008/100456 (PCT/US2008/001765.
Compounds that act as antagonists of the alpha-2C receptor are also known in the art. Hoeglund et al. describe quinoline derivatives that are said to be potent and selective alpha 2C antagonists and said to be useful in treating “certain psychiatric disorders such as depression and schizophrenia” (Hoeglund et al., J. Med. Chem 49:6351-6363 (2006)). WO 2001/64645 to Orion Corp. also describes quinoline derivatives that are alpha-2C receptor antagonists and indicates that these compounds are useful for the treatment of conditions of the pheripheric or CNS system, including treating depression, anxiety, post traumatic stress disorder, schizophrenia, Parkinson's disease and other movement disorders, and dementias (e.g., Alzheimer's disease). WO 2003/082825, also to Orion Corp., indicates alpha-2C receptor antagonists have utility in treating symptoms of disorders and conditions with sensorimotor-gating deficits. Selliner et al., indicate that acridin-9-yl-[4-(4-methylpiperazinal-1-yl)phenyl]amine is a highly selective alpha-2C adrenergic receptor antagonist and may be useful intreating neuropsychiatric disorders (Salliner et al., British J. Pharmacol. 150:391-402 (2007)).
It is also known that compounds having adrenergic activity, such as α2A agonists, may be associated with undesirable side effects. Examples of such side effects include hyper- and hypotension, sedation, locomotor activity, and body temperature variations.
Cordi et al. in U.S. Pat. Nos. 5,436,261, 5,486,532 and 5,648,374 describe benzospiroalkene heterocyclic compounds of the general formula
that are said to be useful as α2-adrenergic agonists; in the compounds described therein the definition of X includes —(CH2)2—, —O—, —O—CH2—, and —S—CH2—; of Y includes —O—, —S—, and —N(R6)—; and of R5 includes hydrogen or an amino group. Cordi et al. also disclose spiro[1,3-diazacyclopent-1-ene)5,2′-(1′,2′,3′,4′-tetrahydronaphthylene)] or spiro-imidazolines compounds such as
in J. Med. Chem. 1994, 38:4056-4069 as α-adrenergic agonists. WO 2006/080890 discloses that this compound may be used in combinations with other agents to prevent biofouling organisms.
U.S. Pat. No. 6,673,337 describes and claims an ophthalmic composition comprising an alpha-2C agonist component and a solubility enhancing component other than cyclodextrin. The patent does not specifically describe alpha-2C receptor agonists.
It has been discovered in accordance with the present invention that the inventive compounds act as modulators of the alpha-2C receptor (i.e., they can act as alpha-2C receptor agonists or as alpha-2C receptor antagonists) and are useful in treating disorders modulated by the alpha-2C receptor.
There is a need for new compounds, formulations, treatments and therapies to treat diseases and disorders associated with α2C adrenergic receptors. Further, there is a need for alpha-2C receptor modulators that minimize adverse side effects, such as those associated with the alpha-2A receptor subtype (viz., blood pressure or sedation). It is, therefore, an object of this invention to provide compounds useful in the treatment or prevention or amelioration of such diseases and disorders.